Fuel line replacement - HELP!

[pierre]

Round hose thru a square passage - what were they thinking?

Bike - '81 R65

Task - I'm replacing the fuel line that goes from the left side of the engine to the right carb.  This seemingly easy operations has take way more time (hours) and effort than I should have. I just hope this truly is the source of the fuel that was dripping onto my exhaust pipes.

Problem - how to thread the round fuel line (with woven cloth protective covering) thru the square passage created where the air injection assembly sits above the transmission.  The fuel line isn't rigid enough to allow the needed pressure to get the line all the way thru.

Am I missing some obvious technique that makes this easy? It would be a first for me.

Do I need to remove the entire air system housing just to replace the fule line?  That just doesn't seem practical.

Will any fuel line with the same ID work.  I think a non-protected rubber hose would go in easier. Perhaps with a little lubrication.  (insert chuckle here)

I tried cutting the leading edge of the fuel line at an angle in hopes of threading it through more easily, but that didn't.  

Thanks,
Pierre

[Bob_Roller]

If you have 1/4th inch diameter steel tubing, or something else you have around the house around 10 inches long, that you can insert into the tubing, then place the steel tubing or whatever you have into the opening and feed it through to the other side, put some dish washing detergent on the hose to lubricate it.

I have used 1/4th inch steel tubing in place of rubber hose going under the airbox.

You can also open up the square hole a bit with a file, and then touch up the paint when your done.

[donbmw]

It is not hard to remove the air box to replace the line. If you use some of the none colth woven fuel line a coat hanger or something else will can help guide the line through the openings.

Don

[pierre]

Thanks for the replies.

Don,
Removing the air box seems to involve removing the suction funnels to the carbs, the steel air lines, and all the innards of the air box to get to the 3 bolts that hold the air box to the trans.  I started down that road initially before thinking "there's got to be an easier way".

Don / Bob
Threading the fuel line thru the passage isn't the problem, per se.  It's that the woven cloth protecting creates friction with the passage way to the point that once the fuel line is about 1/3 of the way in it's stuck and can't be pushed any more.  I can't even rotate it.  It's just that tight.  So the wire coat hanger guide or the 1/4 inch steel tubing won't help.  

I'll give the dish washing detergent a try tomorrow. Just have to be careful not to get any inside the fuel line or I'll have bubble coming out of my exhaust as I ride down the road.  

[nhmaf]

I believe most everyone uses the either the vinyl or rubber fuel line which doesn't have the woven exterior for the crossover fuel hose hookups.  IT is much easier to thread through the slot - and using a coat hanger or similar wire from the other side also helps with guiding it through.

[Justin B.]

Use the polyurethane 1/4" tubing and it will slip through with room to spare...  Your rubber stuff will quickly start deteriorating with the high levels of ethanol now used in gas...

[drewboid]

If I recall correctly BMW fuel hose is 6mm - just a slight bit smaller than 1/4 inch. If you are using US standard hose it is too large! The 1/4 inch hose also does not fit the taps as tightly and may leak without a clamp.
Just a thought.

[Justin B.]

I've been using 1/4" line for years without any problems.  I concur that 1/4" is a bit larger than 6 mm but I've not seen any problems - at least with the line I use...

[Lucky_Lou]

As this is something that you wont need to do to often i would recommend you remove the air box and fit a protected line its no big deal and everything fits back together easilly the fuel tap side of the airbox is retained on a clip and just pushes back into place do it right first time and you wont have to worry about it again you souldnt have to strip it off the breather tubes to give you enough room for feeding the pipe through....whatever pipe you choose make sure it doesnt go brittle with fuel.(bear in mind this section of pipe gets quite hot and is subject to alot of vibration) i would stick to the fabric covered rubber tube if i were you it doesnt cost that much.
Lou  

[Bob_Roller]

I did a little metric to SAE conversion between 6mm, and 1/4 th in. diameter, and came up with the 1/4 th in. fuel line is .35 mm larger ( .0135 in.) than 6mm.

Not enough to get concerned about.

After the BMW cloth hose wasn't available from the dealer anymore, I've been using NAPA auto parts 1/4th in. common fuel line, and I have never had a problem with the lines leaking, failing, coming off or degrading due to ethanol in the fuel supply.

I replace the lines every 3-4 years.

I've never used hose clamps on any of the connections.

I heat up the fuel line with a hair dryer, put a light oil, or petroleum jelly on the metal fittings, and put them together.

When it comes time to remove them, I always have to cut them off, they never come off willingly.

[Justin B.]

The nice thing about the urethane line is you just hack it to length, spit in the end, and it slides right over the barb!

I have added a 1/4" steel tube crossover on one bike just to say I'd done it to one, it seems to be working just fine.  I cut some 1/4" line to length and put just the slightest flare on each end using a double-flaring tool.  Slide on the hoses and mod is finished...

[montmil]

I also use the NAPA 1/4" fuel line on both the R65s with no problems, mon.

I straightened out a coat hanger wire, fed it thru the square hole, then slipped the fuel hose over it. A bit of silicone spray lubricant on the hose exterior made the install a non-event.

Monte